a-InGaZnO Thin-Film Transistor-Based Operational Amplifier for an Adaptive DC–DC Converter in Display Driving Systems

摘要

In this paper, we present an operational amplifier (op-amp) and a pulsewidth-modulation (PWM) controller fabricated with amorphous indium–gallium–zinc oxide thin-film transistors (a-InGaZnO TFTs), to build an adaptive dc–dc converter for display driving systems. The fabricated a-InGaZnO TFT presents electrical characteristics suitable for accomplishing an op-amp composed only with n-type TFTs to have an overall gain of 24.5 dB, a cutoff frequency of 6 kHz, and a unit gain frequency of 32 kHz operating at ±15 V. The fabricated op-amp is used to construct a comparator and an error amplifier on the glass, which are combined to realize a PWM controller. The resulting PWM controller can successfully control the output voltage of an external dc–dc converter that follows the input voltage to the error amplifier, and can operate at 100 Hz to control the duty ratio from 24.3% to 66.1% when the reference voltage varies from 2 to 6 V, respectively.